The present disclosure relates to a reception apparatus, a reception method and a program, and particularly to a reception apparatus, a reception method and a program which are ready for both of data transmission for which a single carrier is used and data transmission for which multi carriers are used.
The DTMB (Digital Terrestrial Multimedia Broadcast) standard is known as a standard for terrestrial digital broadcasting. In the DTMB standard, one of a modulation method for which a single carrier is used and another modulation method for which multi carriers are used can be selected as a modulation method for data.
In the following description, data transmission by the modulation method for which a single carrier is used is suitably referred to as single carrier transmission, and data transmission by the modulation method for which multi carriers are used is suitably referred to as multicarrier transmission.
Upon single carrier transmission, data transmission in compliance with the DTMB standard is carried out such that a PN signal and a data signal are transmitted periodically. On the other hand, upon multicarrier transmission, data transmission is carried out such that data obtained by carrying out IFFT (Inverse Fast Fourier Transform) arithmetic operation for a PN signal and a data signal are transmitted periodically. The PN signal is a known signal configured from a predetermined data string and is inserted as a guard interval for preventing interference between data signals.
A reception apparatus which is ready for the DTMB standard includes an equalizer for receiving data transmitted by single carrier transmission and another equalizer for receiving data transmitted by multicarrier transmission.
Configuration of the Single Carrier Equalizer
FIG. 1 shows a configuration of a single carrier equalizer for receiving data transmitted by single carrier transmission.
Referring to FIG. 1, a circuit at a stage preceding to the single carrier equalizer carries out frequency conversion of a reception signal and carries out such processes as A/D (Analog/Digital) conversion, orthogonal demodulation and so forth for an IF signal obtained by the frequency conversion. An input signal ID(t) obtained by such various processes by the preceding stage circuit is inputted to a feedforward equalizer (FFE 11 and a least mean square (LMS) arithmetic operation section 16. In the single carrier equalizer, the FFE 11 and a feedback equalizer (Feed Back Equalizer: FBE) 14 are used to carry out equalization for a signal in the time domain.
The FFE 11 includes a variable coefficient filter and uses a coefficient C0(n) determined by the LMS arithmetic operation section 16 to carry out convolution arithmetic operation between the input signal ID(t) and the coefficient C0(n). The FFE 11 outputs a signal OD0(t) representative of a result of the convolution arithmetic operation to an addition section 12. If the tap number of the FFE 11 is represented by N_FFE, then the output signal OD0(t) of the FFE 11 is represented by the following expression (1):
                              OD          ⁢                                          ⁢          0          ⁢                      (            t            )                          =                              ∑                          i              =              0                                                      N                ⁢                _                ⁢                FFE                            -              1                                ⁢                                    ID              ⁡                              (                                  t                  -                  i                                )                                      ×            C            ⁢                                                  ⁢            0            ⁢                          (              i              )                                                          (        1        )            
The addition section 12 adds the output signal OD0(t) of the FFE 11 and an output signal OD1(t) of the FBE 14 to produce an equalized signal OD(t) (OD(t)=OD0(t) and OD1(t)) and outputs the equalized signal OD(t). The equalized signal OD(t) outputted from the addition section 12 is outputted to the outside of the single carrier equalizer and is supplied also to a hard decision section 13 and an error calculation section 15.
The hard decision section 13 carries out a hard decision of the equalized signal OD(t) supplied thereto from the addition section 12 and outputs a signal OD′(t) representative of a result of the hard decision. The signal OD′(t) is supplied to the FBE 14, the error calculation section 15 and a LMS arithmetic operation section 17.
Also the FBE 14 is formed from a variable coefficient filter and uses a coefficient C1(n) determined by the LMS arithmetic operation section 17 to carry out convolution arithmetic operation of the signal OD′(t) supplied thereto from the hard decision section 13 and the coefficient C1(n). The FBE 14 outputs a signal OD1(t) representative of a result of the convolution arithmetic operation. The output signal OD1(t) is supplied to the addition section 12, by which it is used for addition to the output signal OD0(t). Where the tap number of the FBE 14 is represented by N_FBE, the output signal OD1(t) of the FBE 14 is represented by the following expression (2):
                              OD          ⁢                                          ⁢          1          ⁢                      (            t            )                          =                              ∑                          i              =              0                                                      N                ⁢                _                ⁢                FBE                            -              1                                ⁢                      0            ⁢                                          D                ′                            ⁡                              (                                  t                  -                  α                  -                  i                                )                                      ×            C            ⁢                                                  ⁢            1            ⁢                          (              i              )                                                          (        2        )            where α is delay time from the equalized signal OD(t) to the signal OD′(t).
The error calculation section 15 subtracts the signal OD′(t) representative of a hard decision result supplied thereto from the hard decision section 13 from the equalized signal OD(t) supplied thereto from the addition section 12 and outputs an error signal E(t) (E(t)=OD(t)−OD′(t)). The error signal E(t) outputted from the error calculation section 15 is supplied to the LMS arithmetic operation section 16 and the LMS arithmetic operation section 17.
The LMS arithmetic operation section 16 carries out LMS arithmetic operation based on the input signal ID(t) and the error signal E(t) supplied thereto from the error calculation section 15 and updates the coefficient C0(n) of the FFE 11.
The LMS arithmetic operation section 17 carries out LMS arithmetic operation based on the signal OD′(t) supplied thereto from the hard decision section 13 and representative of a hard decision result and the error signal E(t) supplied thereto from the error calculation section 15 and updates the coefficient C1(n) of the FBE 14.
In this manner, the single carrier equalizer carries out hard decision arithmetic operation which is arithmetic operation for equalization of the input signal ID(t), arithmetic operation of an error signal and arithmetic operation for updating of the coefficients of the variable coefficient filters, that is, the FFE 11 and the FBE 14, using signals in the time domain. It is to be noted that “(t)” represents that the pertaining signal is a signal in the time domain.
Configuration of the Multicarrier Equalizer
FIG. 2 shows a configuration of a multicarrier equalizer for receiving data transmitted by multicarrier transmission. Referring to FIG. 2, an input signal ID(t) is inputted to a PN removing section 21.
The PN removing section 21 subtracts an estimation value PN′(t) of a PN signal supplied thereto from a channel estimation section 28 from the input signal ID(t) to remove the PN signal from the input signal ID(t) and outputs a data signal (ID(t)−PN′(t)) to a FFT (Fast Fourier Transform) arithmetic operation section 22.
The FFT arithmetic operation section 22 carries out FFT arithmetic operation for the data signal supplied thereto from the PN removing section 21 and outputs a data signal D(f) to a division section 23. Since the data signal transmitted by multicarrier transmission has been subjected to IFFT (Inverse Fast Fourier Transform) arithmetic operation by the apparatus on the transmission side, the multicarrier equalizer carries out FFT arithmetic operation for the data signal. The data signal D(f) is a signal in the frequency domain.
A division section 23 divides the data signal D(f) supplied thereto from the FFT arithmetic operation section 22 by a channel estimation value H(f) supplied thereto from a LMS arithmetic operation section 26 to produce an equalized signal OD(f) and outputs the equalized signal OD(f). The equalized signal OD(f) outputted from the division section 23 is outputted to the outside and supplied also to a hard decision section 24 and the LMS arithmetic operation section 26.
The hard decision section 24 carries out a hard decision of the equalized signal OD(f) and outputs a signal OD′(f) representative of a result of the hard decision to an error calculation section 25.
The error calculation section 25 subtracts the signal OD′(f) supplied thereto from the hard decision section 24 from the equalized signal OD(f) and outputs an error signal E(f) (E(f)=OD(f)−OD′(f)) to the LMS arithmetic operation section 26.
The LMS arithmetic operation section 26 carries out LMS arithmetic operation based on the equalized signal OD(f) supplied thereto from the division section 23 and the error signal E(f) supplied thereto from the error calculation section 25 to determine a channel estimation value H(f) in the frequency domain. The channel estimation value H(f) determined by the LMS arithmetic operation section 26 is supplied to the division section 23, by which it is used for equalization of the data signal D(f). The channel estimation value H(f) is supplied also to an IFFT arithmetic operation section 27.
The IFFT arithmetic operation section 27 carries out IFFT arithmetic operation for the channel estimation value H(f) supplied thereto from the LMS arithmetic operation section 26 and outputs a channel estimation value C(n) in the time domain to the channel estimation section 28.
The channel estimation section 28 is formed from a variable coefficient filter and uses the channel estimation value C(n) supplied thereto from the IFFT arithmetic operation section 27 as a coefficient to carry out convolution arithmetic operation of a PN signal PN(t) reproduced by a PN reproduction section 29 and the channel estimation value C(n). The channel estimation section 28 outputs an estimation value PN′(t) determined by the convolution arithmetic operation to the PN removing section 21. If the PN signal reproduced by the PN reproduction section 29 is represented by PN(t) and the tap number of the filter which configures the channel estimation section 28 by N_CHE, then the estimation value PN′(t) of the PN signal is represented by the following expression (3):
                                          PN            ′                    ⁡                      (            t            )                          =                              ∑                          i              =              0                                                      N                ⁢                _                ⁢                CHE                            -              1                                ⁢                                    PN              ⁡                              (                                  t                  -                  i                                )                                      ×            C            ⁢                                                  ⁢                          (              i              )                                                          (        3        )            
The PN reproduction section 29 reproduces the PN signal PN(t) and outputs the reproduced PN signal PN(t) to the channel estimation section 28.
In this manner, the multicarrier equalizer carries out hard decision arithmetic operation which is arithmetic operation for equalization of the input signal ID(t), arithmetic operation of an error signal and arithmetic operation for updating coefficients of the variable coefficient filter, that is, the channel estimation section 28, using signals in the frequency domain. It is to be noted that “(f)” indicates that the pertaining signal is a signal in the frequency domain.
The following Non-Patent Documents are available as related art documents:
A Combined Time and Frequency Algorithm for Improved Channel Estimation in TDS-OFDM, Liu, M.; Crussiere, M.; Helard, J.-F.; Communications (ICC), 2010 IEEE International Conference on;
Novel Synchronization for TDS-OFDM-Based Digital Television Terrestrial Broadcast System, Zi-Wei Zheng, Zhi-Xing Yang, Chang-Yong Pan, and Yi-Sheng Zhu, Senior Member, IEEE, IEEE TRANSACTIONS ON BROADCASTING, VOL. 50, NO. 2, JUNE 2004; and
Error rotated decision feedback equalizer for Chinese DTTB Receiver, Dazhi He; Weigiang Liang; Wenjun Zhang; Ge Huang; Yunfeng Guan; Feng Ju; Broadband Multimedia Systems and Broadcasting, 2008 IEEE International Symposium on.